FIG. 1 is a diagrammatic, side view of an illustrative, conventional tone arm structure during playback. In the FIG. 1 is an arm shaft, 2 is a head shell, 3 is a weight and 4 is an arm shaft holder. The material used in arm shaft 1 ought to be physically strong and of light weight. Generally, metal pipe is used. In addition, sheet like arm shafts may be used whose cross-sections are three sided squares. However, the following problems arise in these conventional arm shafts due to the connection from head shell 2 to arm shaft holder 4 and weight 3.
In FIG. 1, a pick up cartridge 5 and its associated needle (which is supported by a cantilever 7) reproduces an audio signal recorded on a record 6. Cartridge 5 is supported by head shell 2. However, lateral wave shape vibration develops in cantilever 7 at this time and longitudinal wave vibration develops at the support of the cantilever. The cause of the foregoing seems to be a longitudinal wave vibration in the direction of damper operation since the damper which statically supports the cantilever and which dampens its vibration resists the lateral wave vibration of the cantilever. The longitudinal wave vibration indicated at 8 is the origin of the oscillation of the generator supported within cartridge 5. It is then conveyed to head shell 2 and to arm shaft 1 where vibration is set up. This is then transmitted to arm shaft holder 4 and weight 3. Parts of the foregoing elements return the vibration to cartridge 5 as a catoptric wave 8' and the generator vibration is repeated. This deteriorates the electrical output signals of cartridge 5 and results in inter-modulation distortion and noise. Thus, the reproduction tone quality is seriously undermined.
Recent counter-measures include tone arm structures which prevent mechanical connection through proper elastic support of the tone arm by head shells and weights which resist vibration and through improvement of the vibration resistant qualities of the generator circuit within the cartridge. Also note Japanese Patent Applications No. 51-23701 entitled "Pick-Up Tonearm" and No. 51-24246 entitled "No-resonance Head-Shell".
However, in the physically important arm shaft 1 which constitutes more than sixty percent of the effective length of the tone arm structure in a conventional record player, there is virtually no mechanical internal loss in propagation of longitudinal wave vibration 8 lengthwise in the arm shaft 1 since, as indicated above, the length involves a smooth connection from the head shell 2 to the arm shaft holder 4. Accordingly, in a conventional arm shaft 1, there is no attenuation in propagation of longitudinal wave vibration 8 in the arm shaft and this vibration easily travels back and forth. Thus, a negative effect on the pick up structure is unavoidable.